Area Forecast Discussion
Issued by NWS Sterling, VA

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720 FXUS61 KLWX 060217 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 917 PM EST FRI FEB 5 2016 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVERHEAD THROUGH SATURDAY. COASTAL LOW PRESSURE WILL PASS BY WELL TO THE SOUTH AND EAST SUNDAY. ANOTHER LOW PRESSURE SYSTEM MAY IMPACT THE AREA MONDAY INTO TUESDAY. THE LOW WILL MOVE AWAY FROM THE AREA DURING THE MIDDLE PORTION OF NEXT WEEK. && .NEAR TERM /THROUGH SATURDAY/... HIGH PRESSURE IS BUILDING INTO THE MID-ATLANTIC FROM THE OHIO VALLEY TONIGHT. WINDS HAVE RAPIDLY DIMINISHED THIS EVENING...ALREADY BECOMING CALM IN MANY LOCATIONS. THIS HAS ALLOWED TEMPERATURES TO QUICKLY TUMBLE...ALREADY NEARING FORECAST LOWS IN SOME OF THE TYPICAL COLD SPOTS. MID-EVENING UPDATE WILL DROP LOW TEMPERATURES BY AT LEAST A DEGREE OR TWO IN MOST LOCATIONS OUTSIDE OF THE URBAN CENTERS. THE ONLY OTHER ISSUE FOR THE NIGHT IS INCREASING CIRRUS ASSOCIATED WITH THE SOUTHERN STREAM JET. HIGH PRESSURE WILL REMAIN OVERHEAD SATURDAY. WINDS WILL BECOME LIGHT AND SOUTHERLY WITH TEMPS REACHING THE MID 40S UNDER PARTLY TO MOSTLY SUNNY CONDITIONS. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... AN UPPER LEVEL TROUGH WILL DIG INTO THE SE US SATURDAY NIGHT AND SUNDAY. COASTAL LOW PRESSURE IS EXPECTED TO DEVELOP OFF THE CAROLINA COAST BY SUNDAY MORNING. ACROSS THE MID-ATLANTIC... HIGH PRESSURE PERSISTS OVERHEAD. CLOUDS WILL INCREASE SATURDAY NIGHT. MOST OF THE MODEL GUIDANCE HAS THE UPPER LEVEL TROUGH PUSHING THE COASTAL LOW OUT TO SEA AND THE MID-ATLANTIC WILL LIKELY NOT BE IMPACTED SUNDAY. CONFIDENCE IS MEDIUM THAT PRECIPITATION WILL STAY SOUTH OF THE REGION SUNDAY. && .LONG TERM /MONDAY THROUGH FRIDAY/... A LARGE AREA OF LOW PRESSURE IN THE UPPER LEVELS SHOULD SPAWN A LOW PRESSURE SYSTEM AT THE SURFACE IN THE MID-ATLANTIC REGION OR CAROLINAS LATE MONDAY INTO MONDAY NIGHT. THIS NEWLY FORMED LOW COULD HAVE A MORE DIRECT IMPACT TO OUR REGION...BRINGING LIGHT TO MODERATE SNOW MONDAY NIGHT WITH COLDER AIR TO SUPPORT THE NEW LOW. A FEW INCHES OF SNOW CANNOT BE RULED OUT. ONE SIMILARITY WITH THE EUROPEAN MODEL AND THE GFS MODEL WITH THIS NEW LOW IS BOTH CLOSE OFF THE NEW LOW NEAR THE MID-ATLANTIC COAST TUESDAY BEFORE PIVOTING IT NORTHWARD TOWARD NEW ENGLAND TUESDAY NIGHT. THE DIFFERENCE IN THE POSITION OF THIS CLOSED LOW WILL DETERMINE WHETHER THE MID-ATLANTIC REGION GETS HIT WITH MODERATE SNOW ACCUMULATIONS OR A MIX OF RAIN AND SNOW SHOWERS WILL LITTLE SNOW ACCUMULATION. AT THIS TIME...THE EUROPEAN MODEL CLOSES THE LOW NEAR THE MOUTH OF THE CHESAPEAKE BAY. THE GFS MODEL CLOSES THE LOW NEAR THE MOUTH OF THE DELAWARE BAY...FARTHER NORTH. WE HAVE A CHANCE OF RAIN OR SNOW IN OUR REGION TUESDAY THEN A CHANCE OF SNOW SHOWERS TUESDAY NIGHT. THE MAIN UPPER LEVEL SUPPORT BEHIND THE COASTAL LOW WILL SLOWLY PIVOT FROM THE OHIO VALLEY...ACROSS THE REGION...AND OFFSHORE WEDNESDAY AND WEDNESDAY NIGHT. SOME UPSLOPE SNOW SHOWERS MAY EXIST IN THE POTOMAC HIGHLANDS WITH COLDER AIR ALOFT PUNCHING INTO THE REGION. A LINGERING SNOW SHOWER MAY BE NEAR THE CHESAPEAKE BAY AS WELL. ELSEWHERE...COLDER AND DRIER AIR WILL FILTER INTO THE REGION AS HIGH PRESSURE BUILDS IN FROM THE WEST. HIGH PRESSURE SHOULD DOMINATE THURSDAY WITH CHILLY AND DRY AIR. THE GFS IS A LITTLE MORE PRONOUNCED WITH AN UPPER LEVEL DISTURBANCE LATE THURSDAY AND THURSDAY NIGHT THAN THE EUROPEAN. AT BEST...THERE COULD BE A FEW SNOW SHOWERS IN PARTS OF THE REGION. THE CONFIDENCE IS LOW. AS FOR FRIDAY...CONFIDENCE REMAINS LOW ON THE WEATHER SINCE THE EUROPEAN MODEL TAKES A STORM SYSTEM ALONG THE OHIO VALLEY INTO THE MID-ATLANTIC REGION WHILE THE GFS MODEL HAS HIGH PRESSURE BEING THE DOMINANT FEATURE. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... HIGH PRESSURE BUILDS TONIGHT...VFR EXPECTED. NW WINDS HAVE DIMINISHED AND SHOULD GENERALLY BE 6 KT OR LESS THROUGH THE NIGHT. HIGH PRESSURE REMAINS IN PLACE SATURDAY THROUGH SUNDAY. VFR CONDITIONS EXPECTED. LIGHT SOUTHERLY FLOW SATURDAY...BECOMING LIGHT NORTHERLY FLOW SUNDAY AS LOW PRESSURE MOVES OFFSHORE (AND SHOULD HAVE LITTLE IMPACT). IFR OR LIFR CONDITIONS MONDAY NIGHT WITH PERIODS OF LIGHT TO MODERATE SNOW. WINDS EAST BECOMING NORTHEAST AROUND 5 KNOTS. MVFR TO BRIEFLY IFR CONDITIONS TUESDAY WITH A CHANCE OF LIGHT RAIN OR LIGHT SNOW. WINDS BECOMING NORTHWEST 5 TO 10 KNOTS. && .MARINE... HIGH PRESSURE BUILDS TONIGHT AND WINDS WILL CONTINUE TO DIMINISH. WILL GO AHEAD AND DROP SCA...AS WINDS ARE NOW GENERALLY BELOW 15 KT...AND BELOW 10 KT IN MANY LOCATIONS. HIGH PRESSURE REMAINS IN PLACE SATURDAY AND SUNDAY. LIGHT NW FLOW WILL BECOME S ON SATURDAY...THEN SWING AROUND TO THE N OR NE ON SUNDAY. WINDS WILL LIKELY INCREASE SUNDAY NIGHT AS A COASTAL LOW DEVELOPS SOUTH OF THE WATERS. SMALL CRAFT CONDITIONS ARE POSSIBLE MONDAY INTO TUESDAY DEPENDING ON THE STRENGTH OF DEVELOPING LOW PRESSURE. && .HYDROLOGY... RIVER LEVELS CONTINUE TO DROP. THE POTOMAC RIVER AT EDWARDS FERRY IS SHOULD FALL BELOW FLOOD STAGE IN THE NEXT SEVERAL HOURS. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...HAS NEAR TERM...ADS/HAS SHORT TERM...HAS LONG TERM...KLW AVIATION...ADS/HAS/KLW MARINE...ADS/HAS/KLW HYDROLOGY...ADS

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